Series of thermal transmission tests were conducted on large wall specimens, which measured 300 by 400 cm (118 by 157 in.), using a calibrated hot box test apparatus. The wall specimens were constructed with concrete masonry units and insulated using various interior insulation systems incorporating extruded and block molded expanded polystyrene (EPS) insulation. An exterior insulated finishing system incorporating extruded EPS insulation was also evaluated. The interior and exterior insulation systems included various methods of attachment of the insulation and finish. The impact of these attachment methods on thermal resistance was studied. Thermal resistance values for the various wall constructions were determined for two different mean temperatures. For some constructions R values were calculated using a standard heat transfer methodology commonly followed throughout the construction industry. The calculated system R values were generally only slightly greater than the measured R values, but for some insulation systems the calculation method significantly overestimated the thermal resistance of the wall construction.